APRS at LARGE SPECIAL Events like DAYTON 3 May 2006 ------------------------------------------------------------------------ For more Dayton detail Recommendations, please see: http://www.ew.usna.edu/~bruninga/aprs/DaytonPilgrimage.txt Here is how events that need to support lots-&-lots of APRS trackers (such as the Dayton Hamvention) should be done so that everyone gets tracked, and the channel is not too overloaded so that users can actually message each other too. The goal here is mutual visibility of everyone locally on RF. (This is how the system works in the LA basin too). 1) Support existing mobile paths (WIDE1-1, WIDE2-2 and WIDE3-3) 2) Any plan that expects mobiles to change anything will fail. 2) Setup a local IGate within direct RF range of the event or one hop 3) Setup a low power alt-input 144.99/144.39 digi for pocket trackers 4) Change settings on ALL local digis that can hear the event direct - Disable WIDEn-N support (turn UIFLOOD or UITRACE OFF) - Set UIDIGI or ALIAS list to WIDE1-1, WIDE2-2, WIDE3-3 - Put something like "Only 1-hop supported" in the BTEXT of each digi The above settings will support up to 100+ stations. The IGate will hear everyone, the digis will ONLY digipeat the visiting mobiles once and will not bring in any out-of-area QRM, and the low-power pocket trackers on .99 will be heard. The advantages of this approach are: 1) No user education is required. 2) Only the local DIGI sysop has to do anything. 3) A D700 mobile digi can do the 144.99 alt-input for pocket trackers 4) One person provides an IGate. 5) Everyone can be seen on 144.39 Of course, users with messasges can easily go multiple directed hops by using a directed path with actual digi calls. This is the advantage of the New-N paradigm. Having greatly simplified APRS PATHS to simply WIDEn and allowing for simple settings of UIDIGI, UIFLOOD and UITRACE, the local sysops can change the network on the fly to match the event. Then easily return to normal the next day. And USERS dont have to do anything... DAYTON ITSELF: Dayton has no high and wide digipeaters near the event. But does have a number of smaller 40 to 160' home stations. THis is excellent for a high density event, since there are no tall digis that are overloaded by hearing everything and they wont be bringing in any outside QRM. If all the local home stations surrounding the event and withing 20 miles of the Hamvention, all supported WIDE1-1, then we would have an excellent high-density APRS network that could easily handle the load of over 100 APRS visitors. See the Dayton map: http://www.ew.usna.edu/~bruninga/aprs/DaytonMap.GIF Good APRS requires good planning like any other comms event... Don't forget, with a little more effort, you can do tracking INDOORS for D7 users or anywhere without a GPS with just 2 or 3 digit entries for any of up to 999 different locations. See http://www.ew.usna.edu/~bruninga/aprs/points.txt And Finally, if the load is still too great and/or there are more than 100 or so users, then the next step is to switch all digis to split frequency with the input on 144.99 and outputs still on 144.39. This way: 1) everyone listens and sees EVERYONE on 144.39 direct and one hop. 2) Nothing from out of area gets in, nor does it QRM any digi input. 3) Even fixed XTAL trackers on 144.39 can still be seen locally direct 4) Uplinks to the digis do not get QRM'd by outputs from the digi Split freq operation more than doubles throughput because not only does it spread the load to two frequencies, but it also avoide collisions on the uplink for better reliability. The digi's beacons should indicate that they are 144.39 +600 digis. Actually, only Dayton or LA is where we could ever see that kind of load. de WB4APR